f73f7f4da5
With this change, an ioctl() call is added to open a character device for a
buffer. The ioctl() number is 'i' 0x91, which follows the
IIO_GET_EVENT_FD_IOCTL ioctl.
The ioctl() will return an FD for the requested buffer index. The indexes
are the same from the /sys/iio/devices/iio:deviceX/bufferY (i.e. the Y
variable).
Since there doesn't seem to be a sane way to return the FD for buffer0 to
be the same FD for the /dev/iio:deviceX, this ioctl() will return another
FD for buffer0 (or the first buffer). This duplicate FD will be able to
access the same buffer object (for buffer0) as accessing directly the
/dev/iio:deviceX chardev.
Also, there is no IIO_BUFFER_GET_BUFFER_COUNT ioctl() implemented, as the
index for each buffer (and the count) can be deduced from the
'/sys/bus/iio/devices/iio:deviceX/bufferY' folders (i.e the number of
bufferY folders).
Used following C code to test this:
-------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <fcntl.h"
#include <errno.h>
#define IIO_BUFFER_GET_FD_IOCTL _IOWR('i', 0x91, int)
int main(int argc, char *argv[])
{
int fd;
int fd1;
int ret;
if ((fd = open("/dev/iio:device0", O_RDWR))<0) {
fprintf(stderr, "Error open() %d errno %d\n",fd, errno);
return -1;
}
fprintf(stderr, "Using FD %d\n", fd);
fd1 = atoi(argv[1]);
ret = ioctl(fd, IIO_BUFFER_GET_FD_IOCTL, &fd1);
if (ret < 0) {
fprintf(stderr, "Error for buffer %d ioctl() %d errno %d\n", fd1, ret, errno);
close(fd);
return -1;
}
fprintf(stderr, "Got FD %d\n", fd1);
close(fd1);
close(fd);
return 0;
}
-------------------------------------------------------------------
Results are:
-------------------------------------------------------------------
# ./test 0
Using FD 3
Got FD 4
# ./test 1
Using FD 3
Got FD 4
# ./test 2
Using FD 3
Got FD 4
# ./test 3
Using FD 3
Got FD 4
# ls /sys/bus/iio/devices/iio\:device0
buffer buffer0 buffer1 buffer2 buffer3 dev
in_voltage_sampling_frequency in_voltage_scale
in_voltage_scale_available
name of_node power scan_elements subsystem uevent
-------------------------------------------------------------------
iio:device0 has some fake kfifo buffers attached to an IIO device.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-21-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
157 lines
5 KiB
C
157 lines
5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _IIO_BUFFER_GENERIC_IMPL_H_
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#define _IIO_BUFFER_GENERIC_IMPL_H_
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#include <linux/sysfs.h>
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#include <linux/kref.h>
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#ifdef CONFIG_IIO_BUFFER
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#include <uapi/linux/iio/buffer.h>
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struct iio_dev;
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struct iio_buffer;
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/**
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* INDIO_BUFFER_FLAG_FIXED_WATERMARK - Watermark level of the buffer can not be
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* configured. It has a fixed value which will be buffer specific.
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*/
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#define INDIO_BUFFER_FLAG_FIXED_WATERMARK BIT(0)
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/**
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* struct iio_buffer_access_funcs - access functions for buffers.
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* @store_to: actually store stuff to the buffer
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* @read: try to get a specified number of bytes (must exist)
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* @data_available: indicates how much data is available for reading from
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* the buffer.
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* @request_update: if a parameter change has been marked, update underlying
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* storage.
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* @set_bytes_per_datum:set number of bytes per datum
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* @set_length: set number of datums in buffer
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* @enable: called if the buffer is attached to a device and the
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* device starts sampling. Calls are balanced with
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* @disable.
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* @disable: called if the buffer is attached to a device and the
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* device stops sampling. Calles are balanced with @enable.
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* @release: called when the last reference to the buffer is dropped,
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* should free all resources allocated by the buffer.
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* @modes: Supported operating modes by this buffer type
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* @flags: A bitmask combination of INDIO_BUFFER_FLAG_*
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*
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* The purpose of this structure is to make the buffer element
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* modular as event for a given driver, different usecases may require
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* different buffer designs (space efficiency vs speed for example).
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*
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* It is worth noting that a given buffer implementation may only support a
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* small proportion of these functions. The core code 'should' cope fine with
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* any of them not existing.
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**/
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struct iio_buffer_access_funcs {
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int (*store_to)(struct iio_buffer *buffer, const void *data);
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int (*read)(struct iio_buffer *buffer, size_t n, char __user *buf);
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size_t (*data_available)(struct iio_buffer *buffer);
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int (*request_update)(struct iio_buffer *buffer);
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int (*set_bytes_per_datum)(struct iio_buffer *buffer, size_t bpd);
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int (*set_length)(struct iio_buffer *buffer, unsigned int length);
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int (*enable)(struct iio_buffer *buffer, struct iio_dev *indio_dev);
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int (*disable)(struct iio_buffer *buffer, struct iio_dev *indio_dev);
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void (*release)(struct iio_buffer *buffer);
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unsigned int modes;
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unsigned int flags;
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};
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/**
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* struct iio_buffer - general buffer structure
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*
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* Note that the internals of this structure should only be of interest to
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* those writing new buffer implementations.
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*/
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struct iio_buffer {
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/** @length: Number of datums in buffer. */
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unsigned int length;
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/** @flags: File ops flags including busy flag. */
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unsigned long flags;
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/** @bytes_per_datum: Size of individual datum including timestamp. */
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size_t bytes_per_datum;
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/**
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* @access: Buffer access functions associated with the
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* implementation.
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*/
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const struct iio_buffer_access_funcs *access;
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/** @scan_mask: Bitmask used in masking scan mode elements. */
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long *scan_mask;
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/** @demux_list: List of operations required to demux the scan. */
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struct list_head demux_list;
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/** @pollq: Wait queue to allow for polling on the buffer. */
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wait_queue_head_t pollq;
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/** @watermark: Number of datums to wait for poll/read. */
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unsigned int watermark;
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/* private: */
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/* @scan_timestamp: Does the scan mode include a timestamp. */
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bool scan_timestamp;
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/* @buffer_attr_list: List of buffer attributes. */
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struct list_head buffer_attr_list;
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/*
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* @buffer_group: Attributes of the new buffer group.
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* Includes scan elements attributes.
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*/
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struct attribute_group buffer_group;
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/* @attrs: Standard attributes of the buffer. */
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const struct attribute **attrs;
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/* @demux_bounce: Buffer for doing gather from incoming scan. */
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void *demux_bounce;
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/* @attached_entry: Entry in the devices list of buffers attached by the driver. */
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struct list_head attached_entry;
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/* @buffer_list: Entry in the devices list of current buffers. */
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struct list_head buffer_list;
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/* @ref: Reference count of the buffer. */
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struct kref ref;
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};
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/**
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* iio_update_buffers() - add or remove buffer from active list
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* @indio_dev: device to add buffer to
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* @insert_buffer: buffer to insert
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* @remove_buffer: buffer_to_remove
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*
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* Note this will tear down the all buffering and build it up again
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*/
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int iio_update_buffers(struct iio_dev *indio_dev,
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struct iio_buffer *insert_buffer,
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struct iio_buffer *remove_buffer);
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/**
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* iio_buffer_init() - Initialize the buffer structure
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* @buffer: buffer to be initialized
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**/
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void iio_buffer_init(struct iio_buffer *buffer);
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struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer);
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void iio_buffer_put(struct iio_buffer *buffer);
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#else /* CONFIG_IIO_BUFFER */
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static inline void iio_buffer_get(struct iio_buffer *buffer) {}
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static inline void iio_buffer_put(struct iio_buffer *buffer) {}
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#endif /* CONFIG_IIO_BUFFER */
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#endif /* _IIO_BUFFER_GENERIC_IMPL_H_ */
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